Regular Expressions

From ben.goodacre.name/tech

Regular expressions and used in Perl, Apache Rewrite, Vim among many other uses.

Regex	Meaning
.	Any single character except a newline
^	The beginning of the line or string
$	The end of the line or string
*	Zero or more of the last character
+	One or more of the last character
?	Zero or one of the last character
(ben\.)?goodacre.name	ben.goodacre.name or goodacre.name
t.e	t followed by any 1 single character followed by e. This will match the , tre , tle , but not te or tale
^f	f at the beginning of a line
^ftp	ftp at the beginning of a line
e$	e at the end of a line
und*	un followed by zero or more d characters. This will match un , und , undd , unddd etc.
.*	Any string without a newline. This is because the . matches anything except a newline and the * means zero or more of these.
^$	A line with nothing in it.
[qjk]	Either q or j or k
[^qjk]	Neither q nor j nor k
[a-z]	Anything from a to z inclusive
[^a-z]	No lower case letters
[a-zA-Z]	Any letter
[a-z]+	Any non-zero sequence of lower case letters
[^qjk]+	Any non-zero sequence that does not contain a q nor j nor k.
jelly|cream	Either jelly or cream
le)gs	Either eggs or legs
(da)+	Either da or dada or dadada or...
\n	A newline
\t	A tab
\w	Any alphanumeric (word) character.
	The same as [a-zA-Z0-9_]
\W	Any non-word character.
	The same as [^a-zA-Z0-9_]
\d	Any digit. The same as [0-9]
\D	Any non-digit. The same as [^0-9]
\s	Any whitespace character: space, tab, newline, etc
\S	Any non-whitespace character
\b	A word boundary, outside [] only
\B	No word boundary

Match a date yyyy-mm-dd

\d{4}-\d{2}-\d{2}

Will also match 9999-99-99 .

Match a time hh:mm:ss

\d{2}:\d{2}:\d{2}

Will also match 99:99:99 .

Match a Mac address

With -'s or :'s

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